The existing method for determining leveling signals for remote elevator monitoring systems uses bar magnets at one floor and a magnetic proximity probe assembly comprising three proximity sensors typically installed on the top of an elevator car for ease of installation and maintenance. The magnets which excite the sensors are installed in a hoistway. Several mounting methods can be employed to affix the magnets. The magnets are typically glued and clamped to the rail.
Monitoring of elevator leveling determines how accurately the elevator car has stopped at a floor and is performed at one master floor in existing monitoring systems. A leveling signal as well as a controller derived direction of travel signal is sent to a counter which maintains a count that is used to keep track of elevator car position in the hoistway. A third signal, sync, is used as a reset to the counter thereby eliminating long term drift in the count caused by noise on a landing signal line.
Currently, the proximity probe assembly consists of three sensors. One sensor is used for determining elevator leveling at the master floor, one senses each landing or floor as the elevator car passes the floor, and the third is used to synchronize the counter. The array of three magnets is aligned so as to excite the three sensors and is typically installed on the first floor. At all other floors, only the magnet that triggers the landing signal is installed. The magnets are typically 15 cm in length.
An installation of the existing method would begin by affixing the magnetic proximity probe assembly to the top of the elevator car. Next, the magnets would be mounted in the hoistway at each floor either on the rail, on brackets, or on string supports. To position the magnets, the installer would, from the top of the elevator car, move the elevator car to the appropriate floor. He would determine that the elevator car is level at the floor by looking down the front of the elevator car and aligning the floor of the elevator car with the floor. This is an inexact method for installation because the width of an opening from the front of the elevator car to a front wall of the hoistway is only a few centimeters while the distance from the installer to the floor is over several meters. However, this is not critical because of the length of the magnets. It is critical that the elevator car be level with the floor when the sensor which detects landing detects the magnet at that floor.
One disadvantage of the current system is that it is inherently inaccurate due to the guesswork involved in determining when the elevator car is level at a floor as well as the positioning of the magnet. A second disadvantage is that the current system is expensive to install relative to the present invention. Another disadvantage is that leveling of the elevator car is performed at only one floor.